I'm pretty sure it is. I believe the technical term is "Misrepresentation". I don't think it would be an easy fight but it seems that you could try to make an argument that they represented the contract as monthly. There are also examples of ToS being declared invalid because no reasonable person read them, this sounds similar where no one is actually reading the fine print.

While this case may be hard I'm pretty sure it isn't "never". For example if you are buying a subscription to a software suite and they sneak into the contract "You also give us your house" that isn't going to fly, even if you signed it.